Method for high scan sputter coating to produce coated, abrasion resistant press plates with reduced built-in thermal stress

ABSTRACT

A press plate for producing decorative laminate from resin impregnated paper, with alumina particles on its pressing surface, is coated with diborides selected from the group consisting of hafnium diboride, molybdenum diboride, tantalum diboride, titanium diboride, tungsten diboride, vanadium diboride, or zirconium diboride or mixtures thereof for making the press plate resistant to scratching using a process wherein the press plate and the sputtering head are moved relative to one another to provide a scanning speed sufficient to give a thermal gradient in the press plate of 50° F. or less, to provide reduced built-in stress and more delocalized heat distribution throughout the press plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to coated, abrasion resistant press platesused in making abrasion resistant decorative laminate, to the coating ofpress plates and to the making of laminate with these press plates.

2. Discussion of the Background

In the manufacture of decorative laminate, layers of resin impregnatedpaper are pressed against press plates under conditions of temperatureand pressure to cure the resin and bond the layers together. A highgloss press plate imparts a high gloss surface to laminate. A texturedsurface imparts a textured surface to laminate. These press plates areextremely uniform, with even microscopic discontinuities beingminimized. The quality of a high gloss polished press plate can bedetermined by viewing reflected images on its surface and scrutinizingthe reflected images for optical discrepancies. Grit on the surface oflaminate causes micro scratching of stainless steel press platesnormally used in the manufacture of decorative laminate, thus destroyingthe micro finish of the press plate. Press plates can also be scratchedby press plate handling equipment and by debris from pressing equipmentor materials used in making laminate. (Laurence U.S. Pat. No. 5,244,375)

Melamine resin coated decorative laminate is pressed at temperatures ofabout 230-310° F. (110-155° C.) and pressures of about 300-2000 psi(20-136 bar) and preferably about 750-1500 psi (51-102 bar). Heating tothese temperatures and cooling to room temperature results insubstantial expansion and contraction of the laminate and of the pressplate. Expansion and contraction of the laminate and press plate willnot be the same, resulting in the movement of grit on the pressingsurface of laminate across the press plate.

It is disclosed in National Electrical Manufacturers Association (NEMA)Standards Publication No. LD 3, that gloss finish laminate has a glossof 70-100+. High gloss textured finish laminate is disclosed as having agloss of 21-40. Black glass with a gloss of 94″1 degrees, measured at anangle of 60 degrees, is disclosed as the NEMA Standard 3.13.2, forcalibrating a gloss meter for 60 degree angle gloss measurements.

Even discontinuities in high gloss press plates that can only be seenwith a microscope can impart visible surface defects to a high glosslaminate surface. Any scratching of high gloss press plates impartsvisible surface defects to high gloss surfaces of laminate and reducegloss level.

Grit on the decorative surface of laminate imparts abrasion resistance,a commercially desirable characteristic of laminate. Particles ofalumina are commonly used as grit in making decorative laminate. TheVickers hardness of alumina is disclosed in “Tribology: Friction andwear of Engineering Materials”, I. M. Hutchings, CRC Press, 1992, to be1800 to 2000. A useful range of particle sizes is about 10 to about 75microns. Grit of about 25-60 microns is preferred. Optimum abrasionresistance is obtained in the particle size range of about 40 to 60microns. (Lane et. al. U.S. Pat. No. 3,798,111)

Alumina having a maximum particle size of 9 microns is disclosed asbeing effective for imparting a wear resistant surface to glossydecorative laminate. Wear resistance is defined as the resistance of aglossy laminate to loss of gloss when the surface of laminate is exposedto the abrasive effects of sliding objects. It is acknowledged that theresulting laminate does not meet NEMA LD 3.01 requirements to beconsidered as abrasion resistant. However, it is disclosed that glossypress plates are not scratched substantially if the grit particle sizeis maintained at less than 9 microns. (Lex et. al. U.S. Pat. No.4,971,855)

The use of a 410 stainless steel press plate hardened by nitriding isdisclosed for making high gloss decorative laminate. After pressing 100sheets of high gloss laminate with 6 micron and 15 micron grit, thegloss of the pressed laminate remained good to very good. The nitridedpress plate exposed to the 6 micron grit was rebuffed after 234 cyclesand produced acceptable laminate quality for at least another 103cycles. Nitrided press plates exposed to 30 micron grit offered limiteddurability. It is disclosed that the 410 stainless steel press plateused for nitriding had a Rockwell, “C” scale hardness of 38-45 and thatthe nitrided surface had a Rockwell, “C” scale hardness of 60-70. Theequivalent Vickers hardness of 410 stainless steel is about 370-440,based on a conversion table published in “Metals Handbook, MechanicalTestings”, Vol. 8, 9th ed., ASM, 1985. The equivalent Vickers hardnessof nitrided 410 stainless steel is about 500-1000, based on a conversiontable published in “Metals Handbook, Mechanical Testing”, Vol. 8, 9thed., ASM, 1985. (Laurence U.S. Pat. No. 5,244,375)

Laminate with 35 micron average particle size alumina at its surface(PGA 822 overlay, available commercially from Mead Corporation) has beenpressed with high gloss press plates coated with titanium nitride. Afterten pressings, the titanium nitride coated press plates had about 15scratches per square centimeter. A control 410 stainless steel pressplate had about 500 scratches per square centimeter. The Vickershardness of titanium nitride is disclosed in “Tribology: Friction andwear of Engineering Materials”, I. M. Hutchings, CRC Press, 1992, to be1200 to 2000.

The control press plate and the press plate on which the titaniumnitride was coated were cut from the same stainless steel pressingplate. The scratches were visible under a light microscope at 40×magnification. Titanium nitride was coated onto 410 stainless steel highgloss press plates in a magnetron sputter coating system. The use of amagnetron sputter coating system for applying a titanium nitride coatingis disclosed in “Multi-Cathode Unbalanced Magnetron Sputtering Systems,”Sproul, Surface and coating Technology, 49 (1991). The use of amagnetron sputter coating system for cleaning the surface that is to becoated is disclosed in “A New Sputter Cleaning System For MetallicSubstrates,” Schiller et. al., Thin Solid Films, 33 (1976).

Additionally, the color of the laminate pressed with the titaniumnitride coated press plate was different than the color of the laminatepressed with the control press plate. An ASTM D 2244 color difference incomparison to a standard of less than (″0.5) )E is considered as anacceptable color match to the standard. The ASTM D 2244 color differencebetween a standard and laminate pressed with the titanium nitride coatedpress plate was greater than (0.5) )E. The titanium nitride coated pressplate and laminate pressed therefrom had a bronze appearance. Thecontrol press plate and the laminate pressed therefrom did not have abronze appearance. Laminate pressed with the control press plate had anASTM D 2244 color difference when compared with the standard of lessthan (0.5))E.

Iron-based cutting tools have been sputter coated with 2-6 microns oftitanium diboride. The sputtering is carried out in an argon or kryptonbeam of ions accelerated to 1300-1800 volts as a broad-beam ion source.A titanium diboride target is arranged as a cathode. The tool is heatedto about 200° C.(392° F.). Sputtering is done under a vacuum of about4-6 milli-Torr. Titanium diboride has an extremely high Vickersmicro-hardness value, typically about 3600, which is not onlyconsiderably higher than other borides but also substantially higherthan other carbides or nitrides. Titanium diboride is also particularlynoted for its high density, e.g., 88% of theoretical density, a lowresistivity of 30 micro-ohms centimeters, a high strength of about40,000 psi, and a coefficient of thermal expansion which is about8.1×10⁻⁶ at the temperature range of 20E-800EC(68-1472EF). (Moskowitz etal., U.S. Pat. No. 4,820,392)

Control conditions for sputter coating are disclosed in Influence ofApparatus Geometry and Deposition Conditions on the Structure andTopographv of Thick Sputtered Coatings Thornton, Journal of VacuumScience Technology, Volume 11, Number 4, (July/August 1974) andSputtering, Thornton et al., Metals Handbook, Ninth Edition, AmericanSociety for Metals, Metals Park, Ohio, 44073, Volume 5, pp 412-416,(1982).

There is a need for a hard coating on a press plates, continuous belt,and other pressing surfaces that imparts a color to laminate having anASTM D 2244 color difference in comparison to a standard of less than(″0.5) )E. There is a need for a coating that can be applied to apressing surface without changing the appearance of the finish on thepressing surface. There is a need for a pressing surface that is notscratched when used in pressing laminate coated with alumina particlesof greater than 10 microns and preferably greater than 25 microns. Thereis a particular need for a pressing surface that is not scratched whenused in pressing high gloss laminate with an ASTM 2457 60 degree anglegloss of greater than 70, when the surface of the laminate is coatedwith 25-60 micron alumina particles.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a methodfor coating a press plate that provides a superior protective hardcoating and that has a more delocalized heat distribution throughout theplate.

A further object of the present invention is to provide a coated pressplate and method for its manufacture that overcome the above-noteddisadvantages in the art.

These and other objects of the present invention have been satisfied bythe discovery of a method of making a planar pressing surface forproducing decorative laminate from resin impregnated paper, comprising:

imparting a desired finish on a planar pressing surface;

removing contaminants from the planar surface; and

coating the planar surface with diborides selected from the groupconsisting of hafniun diboride, molybdenum diboride, tantalum diboride,titanium diboride, tungsten diboride, vanadium diboride, or zirconiumdiboride or mixtures thereof in a planar magnetron sputter coatingsystem to a Vickers hardness of at least 2000, wherein the coating stepis performed by causing said planar surface and a sputtering head of theplanar magnetron sputter coating system to move relative to one anotherat a scanning speed sufficient to provide a thermal gradient in theplanar pressing surface of 50° F. or less.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to an improved method for production of acoated press plate, particularly a diboride coated press plate. It hasbeen discovered that the color, gloss and surface appearance of laminatemade with pressing surfaces coated with diborides selected from thegroup consisting of hafnium diboride, molybdenum diboride, tantalumdiboride, titanium diboride, tungsten diboride, vanadium diboride, orzirconium diboride or mixtures thereof are substantially the same as thecolor and gloss of laminate made with the pressing surfaces before thecoating is applied. The preferred diborides for coating laminatepressing surfaces are titanium diboride or zirconium diboride. The mostpreferred diboride for coating laminate pressing surfaces is titaniumdiboride. It is believed that titanium diboride is more commonly usedcommercially for coating surfaces than other members of the diborides ofthis invention because it can be sputter coated in a magnetronsputtering system at a higher deposition rate.

Grit, e.g., alumina particles, on the pressing surface of abrasionresistant decorative laminate can scratch press plates and reduce thevisual quality of laminate thereafter made with the press plate. Pressplates of this invention are particularly useful in making abrasionresistant high gloss decorative laminate.

The diboride coating of this invention can be applied on laminatepressing surfaces to have a Vickers hardness of at least 2000 andpreferably at least 2200, sufficient for pressing laminate with 25-60micron or larger alumina particles at the pressing surface of thelaminate without being scratched. A coating of about 3 microns hassufficient hardness to resist scratching by alumina particles on thepressing surface of laminate. The hardness of the coating can becontrolled in a planar magnetron sputter coating system by those skilledin the use of these systems.

It has been discovered that the diboride coating of this invention canbe coated on a pressing surface with sufficient bond strength for use inpressing high pressure laminate. A minimum bond strength of 1.6 andpreferably 1.8 kilogram force (kgf) determined by diamond scratchingbond testing is believed sufficient. Diboride coatings of greater than 6microns can have lower bond strengths due to stresses produced duringcoating.

Bonding of the diboride coating of this invention to the pressingsurface is enhanced by thoroughly cleaning the pressing surface beforeintroducing the pressing surface into a magnetron sputter coatingsystem. Bonding is further enhanced by etching the pressing surface withthe magnetron sputter coating system prior to applying the titaniumdiboride coating. Cleaning, anodic etching, cathodic etching and etchingwith radio frequency (RF) can be accomplished by methods known to thoseskilled in the use of a magnetron sputter coating system. It has beendiscovered that a layer of titanium applied directly onto the pressingsurface before applying the diboride coating of this invention furtherenhances the bonding of the diboride. Improving bonding by cleaning,etching and the use of an intermediate layer between the coating andsubstrate are known to those skilled in the art of using magnetronsputter coating systems.

The coating of press plates in accordance with the present invention canbe performed either in a stationary mode or in a scanning mode. In thestationary mode, the magnetron sputtering is performed with both thesputtering head and the press plate stationary. However, sputtering in astationary mode has been found to provide Vickers microhardness values(HV) of only up to about 1000.

A preferred method for coating the press plate of the present inventionis to perform the coating process in a scanning mode, either by movingthe press plate while keeping the sputtering head stationary or bymoving the sputtering head while keeping the press plate stationary. Thepreferred mode for the scanning process is by moving the sputteringhead. When the scanning process is used, the resulting coated pressplate has been found by the present inventors to have much higher HVvalues (>2000) at similar film thicknesses. In addition, when using thescanning process, the resulting film has increased adhesion, on theorder of 1.6 kgf or higher.

One drawback with the scanning process in a large production size vacuumcoater for press plates of 4′×8′ dimensions, is that even though thefilm properties are similar to the small scale coaters at speeds of2′/min, the press plate can undergo warping due to high thermalgradients (on the order of 100° F. and higher) induced in the pressplate during the process. It has now been found that the thermalgradient induced in the plate can be reduced by an order of magnitude ormore by increasing the scanning speed on a 4′×8′ plate, to a speed offrom 48″/min to 160″/min, preferably from 50″/min to 100″/min, mostpreferably from 55″/min to 80″/min. Within the context of the presentinvention, the scanning speeds are given in linear inches per minutealong the scanning direction, with a sputtering head that has reachescompletely across the short direction of the press plate, typically 4′in a production line. However, other methods of scanning are alsopossible with smaller sputtering heads. Such sputtering heads would beoperated at similar linear speeds, but would require multiple passes toprovide a single complete coating layer. In addition, the reduction inthermal gradient can be achieved while surprisingly maintaining the samefilm properties in the coated plate.

Modeling studies by the present inventors have shown that the thermalgradient can be reduced from 302° F. at 8″/min down to 13° F. at160″/min. This reduction in thermal gradient has been experimentallyconfirmed by producing a coated press plate at scanning speeds of79″/min and 35″/min, giving thermal gradients of 0° F. (or negligible)and about 9° F., respectively.

This ability to reduce the thermal gradient and thus provide a moredelocalized heat distribution throughout the plate is critical becausebuilt-in stress and a limited ceiling temperature for the press plateitself are practical limitations that must be considered in anyproduction scale process. The thermal gradient in the present highscanning speed process is 50° F. or less, preferably 35° F. or less,more preferably 25° F. or less, most preferably 15° F. or less.

EXAMPLES

Black, high gloss, high pressure laminate was pressed with titaniumdiboride coated press plates shown on Table 1. These press plates hadbeen finished for imparting an ASTM D 2457 60 degree angle gloss ofabout 100 to laminate before being coated with titanium diboride. TheASTM D 2244 color difference between a standard and laminate pressedwith the titanium diboride coated press plates shown on Table 1 was lessthan (0.5) ΔE. Gloss and color differences on Table 1, are averages ofmeasurements made on 10 laminates.

TABLE 1 Gloss and Color Differences Press Plate ASTM Gloss @ 60° ASTMColor Difference, ΔE 3000-1 101 0.20 3000-2 100 0.25 6000-1 101 0.356000-2 103 0.40 6000-3 102 0.30 6000-4 102 0.40 6000-5 103 0.45 6000-6101 0.45

Additionally, high gloss Press Plate 3000-2 and a control press platehave been used in the pressing of 760 sheets of high pressure, black,high gloss laminate with 35 micron average particle size aluminaparticles on its pressing surface. Laminate was pressed with these pressplates at about 1000 psi (68 bar) and 280° F. (138° C.). The pressingsurface of the laminate is commercially available overlay sheet with 35micron alumina grit (PGA 822 from Mead). Press Plate 3000-2 and thecontrol press plate were cut from a high gloss, 410 stainless steelpress plate that had been finished for imparting an ASTM D 2457 60degree angle gloss of about 100 to laminate. Press Plate 3000-2 and thecontrol press plate measure about twelve inches along one side andeleven inches along their other side. Press Plate 3000-2 was coated withabout five microns of titanium diboride in a magnetron sputter coatingsystem. The titanium diboride coating was applied in 17 scans, applyingabout 3000 angstroms of titanium diboride per scan. The other was usedas a control.

The first sheet of black, high gloss laminate with 35 micron averageparticle size alumina particles on its pressing surface pressed with thecontrol press plate had an ASTM D 2244 color difference in comparison toa standard of about (0.25)ΔE. The first sheet of black, high glosslaminate pressed with Press Plate 3000-2 had an ASTM D 2244 colordifference in comparison to a standard of about (0.15) ΔE.

The first sheet of black laminate pressed with the control press platehad an ASTM D 2457 60 degree angle gloss of about 100 to laminate. The760th sheet of black laminate pressed with the control press plate hadan ASTM D 2457, 60 degree angle gloss of less than 70. The control pressplate imparted a 60 degree angle gloss of less than 90 to black laminateafter it had pressed about 160 sheets. It is believed that laminate witha 60 degree angle gloss of less than 90 is not commercially acceptableas a high gloss laminate.

These 760 sheets of black laminate pressed with Press Plate 3000-2 hadan ASTM D 2457 60 degree angle gloss of about 100. Press Plate 3000-2has been viewed under a microscope for scratches after pressing these760 sheets of black laminate and none have been found. The control pressplate is heavily scratched.

No differences were observed in the surface appearance of laminatepressed with the Press Plates shown on Table 1 and control press plates.

Titanium diboride was coated onto the high gloss press plate in amagnetron sputter coating system under a number of conditions It is alsobelieved that a coating of at least 3 microns is necessary for achievinga Vickers hardness of at least 2000 and that adhesion decreases atcoating thicknesses of 6 microns or greater. Hardness and adhesion canbe controlled, as known to those skilled in the art, by the pressure andtemperature under which press plates are coated with the diborides ofthis invention and the power (amperes and volts) used in coating thediborides of this invention on press plates.

A textured press plate coated with titanium diboride, hereinafter “PressPlate 3000-3”, and a control press plate been used in the pressing ofgreater than 450 sheets of high pressure, black, textured laminate with35 micron average particle size alumina particles on its pressingsurface. This laminate was pressed at about 1000 psi (68 bar) and 280°F. (138° C.). Press Plate 3000-3 and the control press plate were cutfrom a textured, 630 stainless steel press plate that had been finishedfor imparting an ASTM D 2457 60 degree angle gloss of about 10 tolaminate. Press Plate 3000-3 and the control press plate measure abouttwelve inches along each side. Press Plate 3000-3 was coated with aboutsix microns of titanium diboride in a magnetron sputter coating system.The titanium diboride coating was applied in 20 scans, applying about3000 angstroms of titanium diboride per scan.

The first sheet of this black, textured laminate pressed with thecontrol press plate had an ASTM D 2244 color difference in comparison toa standard of about (0.22) ΔE. Black, high gloss laminate pressed withPress Plate 3000-3 had an ASTM D 2244 color difference in comparison toa standard of about (0.08) ΔE.

The first sheet of this black laminate pressed with the control pressplate had an ASTM D 2457, 60 degree angle gloss of about 9.5. The 450thsheet of this black laminate pressed with the control press plate had anASTM D 2457, 60 degree angle gloss of about 8. This black laminatepressed with Press Plate 3000-3 had an ASTM D 2457, 60 degree anglegloss of about 10.

No differences were observed in the surface appearance of laminatepressed with the Press Plate 3000-3 and a control press plate.

The press plates on Table 1 and Press Plate 3000-3 were cleaned and thenetched under radio frequency conditions in a planar magnetron sputtercoating system. These press plates were then coated with titaniumdiboride in the magnetron sputter coating system under the followingaveraged conditions.

Cleaning chemical cleaning wipe with ethanol, trichloroethane andacetone physical cleaning 5 minute nitrogen gas blow over press plateRadio Frequency Etching Conditions gas medium argon in./ minute (cm./minute) scan speed  1(2.54) mTorr 10 mA/sq. in. (mA/sq. cm.)  3.5(.54)kV  .75 Titanium Diboride Coating Conditions gas medium argon in./minute (cm./ minute) scan speed  1(2.54) mTorr  7 mA/sq. in. (mA/sq.cm.) 83(13) kV  .3

Coating Conditions and Properties Scan Rate Thickness Adhesion HardnessPress Plate _/scan Scans microns kgf kgf 3000-1 3000 14 4.2 1.7 22803000-2 3000 17 5.1 2.1 2830 3000-3 3000 20 5.5 2.0 2700 6000-1 6000 63.7 1.8 1940 6000-2 6000 6 3.7 1.8 2160 6000-3 6000 7 4.4 1.8 22506000-4 6000 7 4.3 2.0 2190 6000-5 6000 10 6 2.2 2880 6000-6 6000 10 62.0 2850 1 micron = 10,000 _(—) units

Three high gloss press plates, measuring about four feet by eight feet,of this invention have been made. These press plates are referred to asPress Plates 3-1, 3-2, and 3-3. These press plates were sputter coatedwith titanium diboride under planar magnetron discharge conditions.

Press Plates 3-1, 3-1, and 3-3 were anodically etched and then coatedwith titanium and titanium diboride in a planar magnetron sputtercoating system under the following averaged conditions. These pressplates were chemically cleaned before they were placed into the sputtercoating system. The temperature of these press plates during etching andcoating was about 300° F.(149° C.). These press plates did not warp atthis temperature.

Cleaning (Press Plates 3-1, 3-2, and 3-3) chemical cleaning wipe withethanol, trichloroethane and acetone (Press Plates Anodic EtchingConditions 3-1, 3-2, 3-3) gas medium argon argon argon in./ minute (cm./minute) scan speed  3(7.6)  3(7.6)  3(7.6) mTorr 25 24 10 mA/sq. in.(mA/sq. cm.)  4.6(.72)  2.9(.45)  2.9(.45) kV  .24  .23  .24 number ofscans  1  1  5 (Press Plates Titanium Coating Conditions 3-1, 3-2, 3-3)gas medium argon argon argon in./ minute (cm./ minute) scan speed 3(7.6)  3(7.6)  3(7.6) mTorr  1.6  1.2  2.7 mA/sq. in. (‘nA/sq. cm.)70(11) 70(11) 70(11) kV  .52  .52  .43 number of Ti scans  1  1  1Titanium Diboride Coating (Press Plates Conditions 3-1, 3-2, 3-3) gasmedium argon argon argon in./ minute (cm./ minute) scan speed   3(7.6)  3(7.6)   3(7.6) mTorr   1.6   1.2   2.7 mA/sq. in. (mA/sq. cm.) 71(11)  75(12) 70(11) kV   .52   .60   .50 number of TiB₂ scans   8  12 18 deposition rate _/scan) 4125 5500 3000 (Press Plates Properties ofTiB₂/Ti Coating 3-1 3-2 3-3) thickness (microns)   3.3   6.6 5.4adhesion (kgf) *   1.2* ** hardness (kgf) 2000 2500 ** *TiB₂/Ti coatingseparated from Press Plates 3-1 and 3-2 during the pressing of laminate.**The hardness and adhesion of Press Plate 3-3 has not been measured.Hardness and adhesion testing destroys the surface of a press plate.

Press Plate 3-3 has been used in the pressing of greater than 1200sheets of high pressure, black, high gloss laminate with 35 micronaverage particle size alumina particles on their pressing surfaces.Press Plates 3-3 was viewed for scratches after pressing these 1200sheets of laminate and none have been found. The titanium diboridecoating on Press Plates 3-1 and 3-2, separated from the stainless steelsubstrate after pressing less than 100 sheets of laminate.

A zirconium diboride coated high gloss press plate of this invention anda control press plate have each been used in the pressing of 10 sheetsof black, high gloss laminate. This laminate had an ASTM D 2244 colordifference in comparison to a standard of about (0.26) ΔE and an ASTM D2457, 60 degree angle gloss of about 100. No differences were observedin the surface appearance of laminate pressed with the zirconium coatedand control press plates.

A zirconium diboride coated high gloss press plate of this invention hasbeen used in the pressing of 10 sheets of black, high gloss laminatewith 35 micron average particle size alumina particles on its pressingsurface. This laminate was pressed at about 1000 psi (68 bar) and 280°F. (138° C.). A commercially available overlay sheet with 35 micronalumina grit (PGA 822 from Mead) is the pressing surface of thelaminate. No scratches were observed on this press plate after thepressing of these 10 sheets of laminate.

This zirconium diboride press plate was cut from a high gloss, 410stainless steel press plate having an ASTM D 2457, that had beenfinished for imparting a 60 degree angle gloss of about 100 to laminate.Two press plates measuring about twelve inches along each side were cutfrom this press plate. One was coated with about five microns ofzirconium diboride in a planar magnetron sputter coating system. Thispress plate was etched under radio frequency conditions for about 15minutes before the titanium diboride coating was applied. A 6 micronzirconium diboride coating was applied in 15 scans, applying about 4,000angstroms of zirconium diboride per scan in a planar magnetron sputtercoating system under the following averaged conditions.

Cleaning chemical cleaning wipe with ethanol, trichloroethane andacetone physical cleaning 5 minute nitrogen gas blow over press plateRadio Frequency Etching Conditions gas medium argon in./ minute (cm./minute) scan speed  1(2.54) mTorr 10 mA/sq. in. (mA/sq. cm.)  3.5(.54)kV  .75 Zirconium Diboride Coating Conditions gas medium argon in./minute (cm./ minute) scan speed  1(2.54) mTorr  7 mA/sq. in. (mA/sq.cm.) 56(9) kV  .4

Black, laminate has been pressed with press plates, measuring six inchesby six inches (15.24 cm×15.24 cm), coated with titanium nitride in amagnetron sputter coating system. The test results shown on Table 3 arethe average results of pressing five sheets of laminate with each pressplate.

TABLE 4 Laminate Pressed With Titanium Nitride Coated Press Platescontrol #8 TiN #8 control #9 TiN #9 ASTM Gloss @ 60° 100 95 100 95 ASTMColor Difference, ΔE 0.30 0.75 0.35 0.90

The gloss of the laminate pressed with the titanium nitride coated pressplate was lower than the gloss of laminate pressed with the controlpress plate. The color of the laminate pressed with the titanium nitridecoated press plate was significantly different from the color of thelaminate pressed with the uncoated control press plate. The titaniumnitride coated press plates and laminate pressed with the titaniumnitride press plates had a bronze appearance.

Black, laminate has been pressed with press plates, measuring six inchesby six inches (15.24 cm×15.24 cm), coated with niobium nitride in amagnetron sputter coating system. The test results shown on Table 4 arethe average results of pressing five sheets of laminate with each pressplate.

TABLE 5 Laminate Pressed With Niobium Nitride Coated Press Plates BlackHigh Gloss Laminate control B3 (3 μm) B5 (5 μm) ASTM Gloss @ 600 106 102101 ASTM Color Difference, ΔE 0.09 0.65 0.85

The gloss of laminate pressed with niobium nitride coated press plateswas lower than the gloss of laminate pressed with the press plate beforeit was coated. The color of laminate pressed with the niobium nitridecoated press plates was significantly different from laminate pressedwith press plates before they were coated.

Black, laminate has been pressed with press plates, measuring six inchesby six inches (15.24 cm×15.24 cm), coated with diamond like coating in amagnetron sputter coating system. The laminate stuck to the diamond likecoated press plate and was destroyed when it was separated.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty that reside in the present invention,including all features that would be treated as equivalents thereof bythose skilled the art to which this invention pertains.

What is claimed is:
 1. A method of making a planar pressing surface forproducing decorative laminate from resin impregnated paper, comprising:imparting a desired finish on a planar pressing surface; removingcontaminants from the planar pressing surface; and coating the planarpressing surface with at least one diboride selected from the groupconsisting of hafnium diboride, molybdenum diboride, tantalum diboride,titanium diboride, tungsten diboride, vanadium diboride, and zirconiumdiboride or mixtures thereof in a planar magnetron sputter coatingsystem to a Vickers hardness of at least 2000, wherein the coating isperformed by causing said planar pressing surface and a sputtering headof the planar magnetron sputter coating system to move relative to oneanother at a scanning speed to provide a thermal gradient in the planarpressing surface of 50° F. or less.
 2. The method of claim 1, whereinsaid scanning speed is selected to provide a thermal gradient in theplanar pressing surface of 35° F. or less.
 3. The method of claim 1,wherein said scanning speed is selected to provide a thermal gradient inthe planar pressing surface of 15° F. or less.
 4. The method of claim 1,wherein said planar pressing surface is stationary and said sputteringhead is caused to move over the planar pressing surface.
 5. The methodof claim 1, wherein said sputtering head is stationary and said planarpressing surface is caused to move beneath the sputtering head.
 6. Themethod of claim 1, wherein said scanning speed is from 48″/min to160″/min.
 7. The method of claim 6, wherein said scanning speed is from50″/min to 100″/min.
 8. The method of claim 7, wherein said scanningspeed is from 55″/min to 80″/min.
 9. The method of claim 1, wherein theplanar pressing surface is coated with diborides in a planar magnetronsputter coating system to a Vickers hardness of at least
 2200. 10. Themethod of claim 1, wherein the planar pressing surface is coated withdiborides selected from the group consisting of titanium diboride,zirconium diboride and mixtures thereof.
 11. The method of claim 1,wherein the planar pressing surface is coated with titanium diboride.12. The method of claim 1, wherein the planar pressing surface is firstcoated with titanium in a magnetron sputter coating system and then withdiborides.
 13. The method of claim 1, wherein the diboride coating has athickness of at least 3 microns.
 14. The method of claim 1, wherein thediboride coating has a thickness of not greater than 6 microns.